If i didn't understand wrong then i think this helps;

During the process just activate a little userform which has label like
"Please wait during the Calculation Process" and leave Userform's ShowModal
property "true". As you know, that means the sheet is visible but unreachable
during the Userform is active.

I think somebody already gave this advise,didn't he?

Anyway, i like simple solutions and hope this simple one works